DE60310420T2 - METHOD FOR PRODUCING DOPED OXID MATERIAL - Google Patents

Abstract

A method for preparing doped oxide material, in which method substantially all the reactants forming the oxide material are brought to a vaporous reduced form in the gas phase and after this to react with each other in order to form oxide particles. The reactants in vaporous and reduced form are mixed together to a gas flow of reactants, which gas flow is further condensated fast in such a manner that substantially all the component parts of the reactants reach a supersaturated state substantially simultaneously by forming oxide particles in such a manner that there is no time to reach chemical phase balances.

Description

The The invention relates to a process for the production of doped oxidic Material according to the preamble of appended claim 1.

A important use finds doped glass material in the light amplification waveguides, such as for example, active optical fibers whose light-amplifying properties based on the application of stimulated emission. To stimulated emissions to enable are the glass material in the core of the active optical fiber and possibly the cladding layer surrounding the core doped with dopants, which are rare earth metals, for example Erbium, is. additionally To optical fibers, the doped glass material in different Types of optical planar waveguides are used.

The Active optical fibers become optical by pulling glass Fibers made from a Faserpreform, wherein the Faserpreform can be made in many different ways. A usual used method for producing a Faserpreform is therein, glass material around a mandrel or a corresponding, rotatably arranged Growing substrate by means of flame hydrolysis deposition (FHD "Flame Hydrolysis Deposition") the above-mentioned growing from the outer periphery of the Faserpreform carried out from In this context, it is often called a so-called OVD procedure (Outer Vapor desposition (method of evaporation from outside) referred to. The FHD process is also used in forming glass layers, that in optical planar waveguides on a planar substrate required are.

At the FHD method becomes common a hydrogen-oxygen flame used as a thermal reactor, and in the production of glass material used glass-forming base materials, such as silicon or germanium tetrachloride, become the burner and the flame usually in a vaporous Condition supplied. The dopants of the glass material, such as Erbium, become the Brenner and the flame usually with carrier gases as vapor or aerosol droplets supplied the corresponding either by evaporation or spraying from the liquid containing dopants are formed.

According to the of Applicant developed solution can the dopants alternatively along the entire path to the burner in liquid Form promoted and e.g. by using hydrogen flow as aerosol droplets not sputtered before reaching the immediate vicinity of the flame is. This method, for example, in the earlier publication WO 00/20346 A1 of the applicant is described in more detail and the considered as a development of the conventional FHD method can be, will later as a liquid flame spraying be designated.

In in the FHD or liquid flame spraying process acting as a thermal reactor flame form the base materials and Dopants further aerosol particles, wherein the aerosol particles be supplied to the substrate to be coated, and so a doped, porous glass material coating form. These aerosol particles are in the literature in English often referred to as "glass soot" on the mandrel or other substrate from a suitable coating layer porous Glass material has grown, the above-mentioned coating layer by heat treatment of the substrate at a suitably high temperature in a sealing glass sintered.

Further is a so-called solution doping method known, wherein in this method one only of base materials Grown Faserpreform before sintering, only after growing the Faserpreform, dipped in a dopant-containing solution becomes.

Rare earth metals are difficult to dissolve in quartz glass and require that, for example, the structure of SiO ₂ -based glass be changed by adding a suitable oxide to the glass. Suitable oxides for these purposes include, for example, Al ₂ O ₃ , La ₂ O ₃ , Yb ₂ O ₃ , GeO ₂ or P ₂ O ₅ . Preferably, this oxide is alumina Al ₂ O ₃ , which simultaneously increases the refractive index of the glass.

At the Doping the core of an optical fiber (or other waveguide) with a rare earth metal is made by the alumina at the same time an increase reaches the refractive index of the core with respect to the cladding layer, which is necessary to realize the functioning of the optical fiber. In the liquid flame spraying method of Applicant is the aluminum by sputtering in a suitable liquid dissolved Aluminum chloride added to the flame. To those for this Use suitable liquids counting for example, water, organic solvents, e.g. ethanol, Methanol, acetone, or mixtures thereof. Used accordingly one for one rare earth metals, e.g. Erbium dissolved in a liquid Nitrate or chloride based sources.

Growing up, as done by the methods described above, when Kie selenium / alumina glass is doped with rare earth metals - the inhomogeneous distribution of dopants in the glass coating forming aerosol particles is a problem. This is z. Caused by the tendency of dopants to form pairs. In a chemical equilibrium erbium does not dissolve in these substances, as individual ions are separated from each other. In the gas phase, erbium tends to oxidize to the form of Er ₂ O ₃ , and in the solid phase erbium usually targets aluminum with a phase system of Al ₅ Er ₃ O ₁₂ + Al ₂ O ₃ . In other words, with aluminum Erbium strives to appear clustered in its own phases. Although the situation in a glassy silica / alumina system is more complex than described above, the preceding discussion gives a good idea of how Erbium works.

Especially when using the liquid-flame method has the biggest part of aluminum and most of it of the erbium, the endeavor to remain in the solid residue particle, that of a liquid one aerosol droplets is generated when it "dries" in the flame, and wherein the above-mentioned oxidation the substances in glass-forming oxides takes place. For this reason, points the Faserpreform forming in the process usually at least two types of soot particles: First, small Si-containing (or Ge-containing) particles that are due to condensation of vaporous base materials and the following to this Evaporation / drying are formed. Second, aluminum and erbium containing residual particles, usually are bigger as the Si particles. Because of these different types of particles The glass material tends to crystallize when sintered.

At the Sintering can also melt some of the crystals, which improves the homogeneity of the glass material. However, there is a risk that the remaining dopants, especially in the larger residual particles, not even then completely Dissolve glass, in this case, considered in miniature, the result in it is that the dopants locally inhomogeneous separated in the glass material are. This weakens the light-enhancing properties of the glass.

on the other hand For example, in the case of one based on a silicon wafer planar waveguide, the temperatures during sintering more limited than in the case of a for optical fibers provided Faserpreform. Thus remain unwanted, scattering causing crystals to be unavoidable even after sintering the finished glass coating, and due to the inhomogeneous composition of the glass material are also the light-enhancing properties of the glass not ideal.

at all such methods, in which Glassootpartikel and in particular Substance-containing particles are not substantially directly through Condensation over a gas phase are generated, but larger liquid aerosol droplets one Intermediate phase, there is a problem in that different Impurities also (encapsulated) remain in the residual particles, resulting from aerosol droplets form.

It the main object of the present invention is a completely new one To propose a method of producing doped oxidic material, the method avoids the problems described above be in the known from the prior art occur.

With the method according to the invention it is possible to produce various oxidic materials. For example, it is possible to produce multicomponent oxidic material in which there are multiple reactants whose respective constituents substantially match, such as, for example, barium titanate (BaTiO ₃ ).

The process may also be used to prepare such multicomponent oxide materials in which there are multiple reactants whose respective proportions are substantially of different sizes, such as piezoelectric PZT (Pb (Zr _{1 -x} Ti _x ) O ₃ ) has a high dielectric constant. (In the formula, the parameter X determines the amount of zirconium and titanium, and a typical value is, for example, 0.45).

With the method according to the invention it is also possible to produce so-called doped oxidic material in which larger amounts of base material and smaller amounts of dopants are present, such as with molybdenum (Mo) doped titanium oxide (TiO ₂ ) and some doped glass materials.

The The aim of this invention is therefore to make it possible to doped oxidic material that is more uniform in quality than before in which the composition is more homogeneous at the micro level than before and in which the crystal structure is present as desired. The different types of properties of the oxidic material be with the invention optimally designed as before, where it possible in this case is to produce better products than before with the oxidic material.

The aim of one embodiment of the invention is to make it possible to produce doped glass material that is equal in quality is more moderate than hitherto, wherein in the glass material no harmful crystallization occurs and wherein the composition of the glass material is homogeneous on the micro level than before. Thus less unwanted light scattering occurs in glass material made in this way, the light scattering causing attenuation / loss of light in the light guides made from the glass material in question. Also, the light-amplifying properties of the glass material are optimally designed with the invention than heretofore, it being possible in this case to produce from the glass material better active optical waveguides, such as active optical fibers than heretofore.

Around To achieve these goals, the method according to the invention is designed as defined in claim 1.

preferred embodiments of the invention are set forth in the other dependent claims.

One essential idea of the invention can be seen therein that all necessary for the production of doped oxidic material Reactants and the base materials and dopants first in a vaporous state, this means into a gas phase. The condensation of the reaction products from the gas phase into one liquid Phase is extremely fast done in such a way all of the doped oxidic material forming reaction products be transferred substantially simultaneously into a supersaturated state, in which case the composition of the thus forming liquid droplet and immediately become very homogeneous from these forming solid particles is trained. Under homogeneous composition of the particles is in this text primarily to understand that different Particles each have the same composition, but also that the local internal composition of a single particle is homogeneous, the is called, that in a single particle all the ingredients evenly over the entire volume of the particle are divided.

According to the invention above, fast Condensation of the constituents of the reactants either by rapid oxidation of the reactants and / or by fast Adiabatic expansion of the gas flow of the reactants achieved.

The conditions according to the invention are set so that the particles are also immediately after the Solidify condensation, leaving no time in this case, to achieve a chemical phase equilibrium.

through the invention it is possible doped oxidic material, such as doped glass material, to make it more homogeneous in composition than So far, in which case the light-amplifying Properties for example in light-enhancing and with rare earth metals doped glass materials better than in the prior art to let. When using, for example, erbium as a dopant is it possible by means of the invention to avoid erbium clustering, and erbium can do so become, more even, preferably as single ions, over to distribute the glass material. In the case of silicon-based planar waveguides, which are made from the crystallization of glass material and the unwanted ones themselves resulting from the crystallization resulting scattering properties Problems avoided. Furthermore, it is possible by means of the invention, such impurities to avoid the in the known from the prior art method tend to encapsulate in the internal parts of the residual particles.

The The invention and some of its advantageous embodiments are described below explained in more detail, the advantages achieved by means of the invention being clear to the person skilled in the art become. In the doped oxide material used in the embodiment according to the means The example set forth in the figures, it is a doped glass material, and based on the associated with it Description may also be made by a person skilled in the art in the production of other doped, oxidic material by possibly making minor changes in the embodiment according to the example Make use. In the following, the invention will be referred to on the attached Drawings described. Show it:

1 a construction of a reactor according to the invention in a basic perspective view;

2 a cross section through the reactor according to the invention, in a schematic representation; and

3 a side view of another reactor of the invention, in a schematic representation.

All reactants required for the preparation of doped glass material according to the invention, as well as the base materials (for example Si or Ge) and dopants (for example Al and rare earth metals) are initially prepared by suitably increasing the temperature of the materials and by choosing a suitable chemical composition Composition for each reactant in a vaporous state, that is converted into the gas phase. The heating of the reactants may be carried out in any manner which would be suitable for the person skilled in the art. For example, silicon tetrachloride may use SiCl ₄ as the base material of the glass material, and aluminum and erbium may be used as dopants, the latter either as nitrates or chlorides. For example, the compounds used as sources of aluminum and erbium may be dissolved in suitable liquids and further vaporized by heating the subject solutions to a gaseous phase. In promoting the gas phase converted reactants, it is possible to use suitable carrier gases.

The Base materials and dopants which are in a gaseous state will be present next mixed together or as separate gas flows B, D supplied to the reactor R, by maintaining its temperature at the same time, that the base materials and dopants B, D in a vapor state remain, as a flow channel acts. The relation between The base materials and the dopants can be modified by changing the ratio the gas flows B, D, for example with the aid of adjustable valves, such as mass flow controllers, or be adjusted in any other suitable manner.

In the reactor R, the gas flow B of the base materials and the gas flow D of the dopants (in 1 at point M) by combining these as the gas flow BD of reactants. Alternatively, the combination and the mixing of the gas flows B, D may have already taken place before the reactor R. It will be obvious to those skilled in the art that the conduits and the like which promote the gas flows B, D and BD and the walls of the reactor R are advantageously heated to prevent significant condensation of the reactants on the walls.

Instead of the conventional, heated pipes and union nozzles, in the furnace-like reactor R according to 1 are arranged, or corresponding, obvious to the expert solutions, it is possible to use when heating and mixing the gas flows B, D of the base materials and the dopants plasma gas, which is generated for example by means of an arc, wherein acting in the carrier gas as the plasma gas Gas flows of the base materials and dopants are mixed.

According to one embodiment The invention will become the hot Gases / vapors the gas flow BD, which are mixed together in the reactor R, oxidized and so very quickly forming in glass material Oxides condensed. The oxidation / condensation is at such a Temperature carried out, in which all reactants assume a multiply supersaturated state. So Condensation takes place immediately, so that - if all reactants and constituents of the dopants are in a supersaturated state - as a result the condensation droplets and immediately form further glass particles P, their mutual and internal composition is homogeneous. Under the inner homogeneous Composition of the particles P is to be understood in this text that the various components in proportion to the total volume of Particles without stratified or other types of locally inhomogeneous Structures divided evenly are.

The relationship the concentrations of the reactants in the particles is in Essentially according to the ratio the concentrations of the reactants in the gas phase in the gas flow BD determined before condensation.

Because it is the material is a glassy material, the it is not a clear melting or solidification temperature the skilled person that the term "condensation" here in another Meaning should be understood. In other words, depending on the circumstances - apparently either a liquid one or form solid glass particles as a result of the condensation.

Around the above explained embodiment To understand the invention, it is important to note that the saturated Vapor pressure of the oxidized forms of the reactants in a determined temperature is considerably lower than in connection with corresponding forms before the oxidation. Because of that can be due to the rapid condensation of the reactants in the gas phase rapid mixing of oxidative gases into the gas flow of the reactants carried out become.

According to the advantageous embodiment of in 1 the condensation / oxidation is carried out by supplying intense radiation O oxidative gases to the reactor, the beams are advantageously arranged transversely to the gas flow BD of the reactants. Preferably, beams O of oxidative gases are also provided on the two opposite walls of the reactor according to FIG 2 arranged such that the gas jets O, which are opposite and adjacent in the cross section of the reactor, are arranged overlapping each other. This increases the turbulence generated by the rays O of oxidative gases in the gas flow BD of the reactants, the turbulences the oxidative gases O and the reaction Efficient mixing of partner gases BD. Radiation O of oxidic gases may also be placed on multiple walls of the reactor R, or they may be directed in some other way that aids in fluidizing and mixing with respect to the gas flow B, D of the reactants.

For example can Oxygen or carbon dioxide can be used as oxidative gases. Oxidative gases O can upon entering the reactor the same temperature as the reactant gases have, so in other words be hot. Thus, the condensation mainly through the change the vapor tension causes the reactants in the oxidation to experience oxides. Advantageously, the oxidative gases However, "cold", what the condensation reinforced and accelerates.

in the Reactor R were created such conditions in which the oxidation reaction partners BD can take place at reaction temperatures, the usual about 1000 to 2000 ° C be. At these temperatures, the course of chemical Reactions determined by the degree of mixing of the gases. In the Practice occurs when the gas flow BD from reactants to the jets O the oxidative gases in the reactor meets, the oxidation in the mixing areas (Reaction areas) that form at the junctions between these gas flows, the "thickness" of these areas usually is about a few millimeters. Of the Reactor R can be used at atmospheric pressure, but the reactions to reinforce can the pressure of the reactor, the flow or the reactants and oxidative gases and the temperature of the reactor be to optimize the process.

At an in 3 In principle illustrated embodiment of the invention, the condensation is brought about by adiabatic expansion of the gas flow BD of reactants. In other words, the gas flow BD is passed by reactants, for example through a known, so-called Lavall nozzle LR. In the Lavall nozzle LR acting as a flow channel and reactor, the gas flow BD can be accelerated to supersonic speed. The oxidative gases O required in the oxidation of the reactants, for example, can be directed to the gas flow BD of the reactants in the narrowest part of the nozzle LR, in which case the turbulence caused by the expansion of the gases intensifies the mixing of the gases. It should be noted that in 3 the illustrative shape of the Lavall nozzle LR does not necessarily coincide with the exact shape of the nozzle actually used.

At the Applying the adiabatic expansion is considered additional Advantage a high speed of particles P achieved at the reinforcement of the Collecting particles on the substrate through the use of Impact mechanisms can be exploited.

With a suitable choice of oxidative gases it is possible to prevent impurities from condensing and in particles end up. For example, you can different types of mixtures of carbon monoxide, carbon dioxide and water can be used as oxidative gases.

Of the Structure of the reactor R, LR may be formed like an oven, such that the walls the reactor to be heated. Advantageously, materials, withstand the high temperatures, e.g. Quartz, as a material of the reactor used. The walls of the reactor partially or completely be porous, in this case, for example, various types of shielding gases through the walls can be passed into the reactor. In the shape of the cross section of the flow channel through the Reactor R, LR is formed, it can be a rectangle, a Circle or another for the Purpose to act appropriate form.

At the It is also possible to form chlorine-free doped glass materials Reaction partners, such as TEOS (tetraethylortosilicate) or GEOS (tetraethoxygermanium), in a suitable form to be used as base materials B. In addition to those mentioned above, it is also possible others rare earth metals and lanthanides as dopants D, for example Neodymium, and also to use phosphorus, boron and / or fluorine.

The glass particles formed by using the method of the invention can according to the state technology on a suitable substrate, for example one be collected rotating mandrel or on a planar substrate, on its surface such a porous one Glass layer is formed, which in later stages in a process compact glass layer can be sintered. The glass particles, however, can also collected by other means, for example as dust powder be that later as required can be used in the manufacture of glass components.

Of course, it will be obvious to one skilled in the art that by combining the modes set forth above in connection with various embodiments of the invention in various ways, it is possible to provide various embodiments of the invention in accordance with the spirit of the invention. Therefore, the examples given above should be It should not be construed as limiting the invention, but these embodiments of the invention may be varied freely within the scope of the inventive features given in the following claims.

In the drawings show only the parts and components the for the understanding of Principles of the invention are important, and it is obvious that, for example, to the temperature and pressure conditions of the reactor R, LR and the gas flows to set certain for the person skilled in obvious components required, but in the Figures are not shown.

Claims (11)

Process for the preparation of doped oxidic Material, the method comprising: - Transferring essentially all Reactant (B, D) in a vapor state in a gas phase by heating the reactants, - Mixing of the reactants (B, D) to produce a gas flow (B, D), - Contacting the gas flow (B, D) with at least one oxidizing agent (O) at a sufficiently high temperature to oxidic particles (P) in one Reaction to form, so that all the reaction products substantially simultaneously a supersaturated Reach state and in the reaction no time remains to to achieve a chemical phase equilibrium. Method according to claim 1, characterized in that that the oxidic material is doped glass material consisting of the base materials (B) and dopants (D) the glass material is formed by making them in the vapor phase in the vapor state react with oxygen to form glass particles (P). Method according to claim 1, characterized in that that the condensation of the oxides by rapid oxidation of the reactants (B, D) is carried out in oxidic particles (B). Method according to claim 3, characterized that the rapid oxidation of the reactants (B, D) by straightening one or more beams (O) of oxidative gases on the gas flow (BD) the reactant, preferably from oxygen and / or carbon dioxide formed rays is achieved. Method according to claim 4, characterized in that that one or more rays (O) of oxidative gases in one Be focused on the gas flow (BD), the strong swirling and mixing caused. Method according to claim 4, characterized in that that the formation of the oxide particles (P) by directing the one or the multiple rays (O) of oxidative gases colder than the gas flow are amplified to the gas flow (BD) of the reactants. Method according to claim 1, characterized in that that the rapid oxidation of the reactants (B, D) into oxidic Particle (P) by adiabatic expansion of gas flow (BD) the reactant is reached and / or enhanced. Method according to claim 7, characterized in that that the gas flow (BD) of the reactants through a Lavall nozzle (LR) or the like is passed. Method according to one of the preceding claims, characterized characterized in that the oxidic material is glass material and an inorganic or organic compound of silicon or germanium, such as silicon tetrachloride or germanium tetrachloride, TEOS (Tetraethylortosilicate) or GEOS (Tetraethoxygermanium) as Reactant (B) is used. Method according to one of the preceding claims, characterized characterized in that the oxidic material is glass material and erbium, neodymium or other rare earth metals, aluminum, Phosphorus, boron and / or fluorine can be used as dopant (D). Method according to one of the preceding claims, characterized characterized in that the oxide particles in a reactor (R) are formed, in which a temperature prevails, approximately in a range between 1000 and 2000 ° C.